Pipes or conduits laid in the ground to provide a service are laid by either of two methods, the open trench method or the directional drilling method.
In open trench method, an open trench is excavated by mechanical machines. The appropriate conduit or pipe is laid in the trench and the trench is backfilled with the excavated soil up to the original level. It is common practice when backfilling the trench to lay a coloured plastic marker tape during the backfilling at some point in the ground above the conduit or pipe. This provides an early warning during any excavation directly over the conduit or pipe, whether this be by manual or machine excavation. The plastic may vary in colour, for example, red for electricity, blue for water, yellow for gas.
However in directional drilling method, a generally horizontal hole is bored in the ground by a drill head guided under the surface of the ground, roadway, footpath or other area from a point of entry to a point of exit without disturbing the surface of the ground there-between. Thus in this method, the coloured marker tape which is normally present in the open trench method is no longer present to provide a warning in the event of later excavation. Thus, up to the present time there is the risk that pipes or conduits laid by the directional drilling method can be damaged during later excavation.
Thus it is an object of this invention to provide an indication in the ground of the presence of a pipe or conduit laid in a hole bored by the directional drilling method.
It is a further object of the invention to provide a visual indication in the ground in the vicinity of a pipe or conduit by a distinctive colour surrounding the pipe or conduit.
A further object of the invention is to provide a method of providing a distinctive colour around or about the pipe or conduit in the soil.
Another object of the invention is to provide apparatus which provides a distinctive colour about the pipe or conduit in the soil.
Also it is an object of the invention to introduce the colour to the borehole fluid or mud during the drilling operation.
Furthermore it is an object of the invention to introduce the desired colour into the borehole during either the pilot bore stage or the back reaming stage, or during both the pilot bore stage and the back reaming stage.